Spinal implant and method of use

ABSTRACT

A spinal implant having a series of sections or units hinged together and a balloon connected to at least some of the sections, the balloon having a curved configuration. The implant has a first delivery configuration and a second curved placement configuration, wherein it has a more linear configuration in the first delivery configuration than in the second curved configuration. The implant assumes the first delivery configuration during delivery to the disc space and maintains the curved configuration after placement within the disc space. The curved configuration can result from filling or expanding the balloon.

This application claims priority from provisional application Ser. No.60/859,357 filed Nov. 16, 2006, the entire contents of which isincorporated herein by reference.

BACKGROUND

1. Technical Field

This application relates to a spinal implant and more particularly to aspinal disc implant that can be inserted minimally invasively.

2. Background of Related Art

After removal of the intervertebral disc, it has been recognized thatthe disc space needs to be filled between the adjacent vertebrae. Thereare two approaches in the prior art to fill the space: one involvingplacement of a fusion cage and the other involving an artificial disc.Fusion cages are essentially metallic cages packed with bone to promotebone ingrowth. The fusion cages, designed to promote fusion, providesupport between the vertebrae, but eliminate motion. Thus, to achievestability, they sacrifice mobility.

Artificial disc prostheses of the prior art take many forms. Each formis essentially designed to strike a balance between sufficient stabilityto support the high loads of the vertebrae and sufficient mobility so asnot to curtail movement of the patient. To date, attempts to strike suchbalance have met with limited success, with the artificial discproviding either stability or mobility, but not both. The need thereforeexists for a disc replacement that can better simulate the natural discby combining adequate support with flexibility.

Additionally, in many intervertebral procedures, major open surgery isrequired. The advantages of endoscopic (minimally invasive) proceduresare well known, e.g. smaller incision causing less trauma and reducedinfection potential, shorter hospital stays, lower costs, reducedpatient recovery time, and reduced pain for the patient. Therefore, itwould be advantageous if such an artificial disc, which achieves abeneficial balance between mobility and stability, could be insertedminimally invasively.

SUMMARY

The present invention provides a spinal implant having a series ofsections or units hinged together and a balloon connected to at leastsome of the sections, the balloon having a curved configuration. Theimplant has a first delivery configuration and a second curved placementconfiguration, wherein it has a more linear configuration in the firstdelivery configuration than in the second curved configuration. Theimplant assumes the first delivery configuration during delivery to thedisc space and maintains the curved configuration after placement withinthe disc space. The curved configuration can result from filling orexpanding the balloon.

In one embodiment, a support strip is positioned on an outer surface ofthe hinged sections. In an alternate embodiment, it is positioned on theinner surface.

In the embodiment wherein a support strip is provided of shape memorymaterial, the support strip can move the hinged sections to the curvedconfiguration, and then the balloon filled to maintain the shape andsupport the sections. Alternatively, both the expanded balloon andsupport can together move the hinged sections to the curvedconfiguration.

In one embodiment, the balloon in the expanded configuration has a firstarea and a smaller area having a smaller transverse cross section, eacharea extending along a length of the balloon.

The present invention also provides a method of minimally invasivelyinserting a spinal implant in a disc space. The method comprisesproviding a delivery instrument containing the spinal implant in a firstconfiguration, the spinal implant having a plurality of hinged sectionsand a balloon connected thereto, inserting the delivery instrument tothe disc space, deploying the implant from the delivery instrument toposition the implant in the disc space, expanding the balloon tomaintain the hinged sections in a substantially horseshoe shapedconfiguration, and removing the delivery instrument and leaving theimplant in place.

In one embodiment the step of expanding the balloon expands the hingedsection in a direction transverse to a plane of the disc space.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiment(s) of the present disclosure are described hereinwith reference to the drawings wherein:

FIG. 1 is a perspective view of a cannula for receiving a disc removaldevice for use in the intra-vertebral space (the soft tissues are notshown);

FIG. 2 is a close up top view of the spinal disc nucleus being removedby a disc removal device;

FIG. 3 is a close up perspective view of a portion (two sections) of animplant device of the present invention;

FIG. 4 is a top plan view of the implant device of FIG. 3 shown in thecurved deployed (placement) position;

FIG. 5 is an exploded view of the portion of the implant of FIG. 3;

FIG. 6 is a close up exploded view of the hinging element of the implantof FIGS. 3 and 4;

FIG. 7 is a plan view of the spinal implant of FIGS. 3 and 4 beingdelivered from the cannula of FIG. 1;

FIG. 8 is a top view of the implant of FIG. 4 shown in place between thevertebral bodies, the drawing further showing the cannula being removed;

FIG. 9 is an enlarged partially exploded view of an alternate embodimentof the implant of the present invention; and

FIG. 10 is a close up perspective view of an alternate embodiment of ahinge for connecting adjacent implant sections.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now in detail to the drawings where like reference numeralsidentify similar or like components throughout the several views,several different embodiments of the spinal implant of the presentinvention are described herein.

The spinal implants of the present invention are designed to be insertedminimally invasively into the disc space, thus enabling a smallerincision to be used in the procedure. This is achieved by the implantsbeing deflectable laterally to a substantially linear configuration.That is, the implant is in a more straightened shape to enable minimallyinvasive insertion through a cannula. Once ejected from the deliveryinstrument at the desired site, i.e. the disc space between adjacentvertebrae, the balloon will be filled and the implant maintained in acurved configuration. Implanted in the disc space, the spinal implant isradially compressible in response to vertebral loads placed thereon.

Turning first to the instrumentation for minimally invasively preparingthe disc space and for minimally invasively delivering the spinalimplant, and with initial reference to FIGS. 1 and 2, a device used inthe intra-vertebral space to remove the spinal disc nucleus in aminimally invasive fashion is illustrated. The disc removal device 10has an elongated tubular portion 12 which is inserted through anarthroscopic cannula 14 and has a pair of cutting jaws 16 which areoperatively connected to and remotely manipulated, i.e. opened andclosed, by a proximal handle (not shown) to cut and remove the discnucleus. Insertion through arthroscopic cannula 14 enables the disc tobe removed minimally invasively rather than through a larger incisionduring an open more invasive surgical procedure.

As the nucleus is removed endoscopically, i.e. through a cannula forminga small incision, the implant of the present invention that is designedto replace the removed disc is also advantageously inserted minimallyinvasively. A delivery instrument (not shown) containing the spinalimplant 30 within a distal portion is inserted through cannula 14.Implant 30 is maintained in the delivery instrument in a substantiallystraightened (linear) configuration.

FIG. 7 illustrates the implant 30 partially ejected from the device;FIG. 8 illustrates the implant 30 fully deployed and implanted in thedisc space. As can be appreciated, as the implant 30 is ejected it movesfrom its more straightened configuration toward its curved configurationdescribed below. After placement of the implant 30, the delivery deviceand cannula are removed from the body.

As can be appreciated in the plan view of FIG. 8, the implant 30 issubstantially horseshoe-shaped or substantially C-shaped inconfiguration as it extends circumferentially along the periphery of thedisc space, thus providing support along the periphery or circumferenceof the disc space. That is, adjacent individual implant sections 32 arelinked and form the curved shaped in a plane defined as lyingperpendicular to the spine and parallel to the disc space definedbetween upper and lower vertebral bodies. It is also contemplated thatthe implant could be a closed loop, e.g. circular, or extend more than360 degrees so the end portions overlap. In each of these instances, theimplant would be delivered in a substantially straighter configurationand move to its curved shape for placement in the disc space.

With reference to FIGS. 3 and 4, the implant 30 is composed of a seriesof sections 32 linked together (only some of which are labeled forclarity). The linked sections 32 can be composed of a shape memorymaterial, stainless steel, or other material to provide sufficientsupport. Each of these sections is preferably C-shaped or U-shaped inconfiguration with a lip 34 formed at the ends of its arms or upper andlower walls 35, 37. A textured surface such as protrusions 36 can beformed on the upper and lower surfaces 38, 39, respectively, of walls35, 37 to increase surface friction between the implant and the opposingbone/vertebrae. Although protrusions are shown, other friction enhancingsurfaces can be provided such as recesses, textured surfaces, differentshaped projections and coatings. The walls 35, 37 can move toward eachother due to the forces of the vertebral bodies between which it isinserted.

Adjacent sections 32 are hinged to enable movement from a more linearconfiguration for delivery through the cannula to the curvedconfiguration shown in FIG. 4. FIG. 6 is an enlarged view of oneembodiment of the hinged structure showing ball 42 received and snappedin a slot formed on the underside of connector 44. This frictionalengagement interlocks adjacent sections 32 while still enabling lateraland pivotal movement with respect to one another.

A support or strut 48 illustratively in the form of an elongated flatstrip is attached to the outer surface 33 of the hinged sections 32,preferably extending along the entire length. This strip 48 ispreferably composed of metal and provides support for the hingedsections and assists in linking of the sections.

In one embodiment, the support is made of shape memory, such as Nitinol,a nickel titanium alloy, although other shape memory metals or polymericmaterials are contemplated, and has a shape memorized configuration of asubstantially horseshoe shape or substantially C-curve as shown in FIG.4. In this manner, the support 48 is maintained in a substantiallystraightened configuration for delivery. Once ejected from the deliverydevice, it will move to its memorized configuration, cooperating withthe balloon explained below to move the hinged sections 32 into thecurved configuration of FIG. 4.

A balloon is designated by reference numeral 50 and shown in theinflated (filled) position in FIGS. 3-5. The balloon has a reduceddiameter section 52 (see arrow D) along its length to fit within theopen arms 35, 37 of the hinged sections 32. The balloon is substantiallyhorseshoe shaped and functions to give the hinged sections thesubstantially horseshoe or curved shape shown in FIG. 4. The largercross-section area 54 has a curved outer surface 56 and remains outsidethe hinged sections 32. A portion abuts lip 34. The balloon is filledwith a gas or liquid after placement of implant 30 in the disc space toexpand and extend in the curved configuration. The substantiallyhorseshoe shape of the balloon thus forces the attached hinged sections32 to form and/or maintain a curved shape, thereby providing the curvedshape to the implant. The balloon 50 can also apply a force against thewalls 35, 37 of the implant 30 (i.e. in a direction transverse to aplane of the disc space) and in some embodiments slightly expands thesewalls to further move surfaces 38, 39 against the vertebrae. The balloonmaterials and pressure can vary to thereby vary the degree ofcompressibility, cushioning and rigidity of the implant. That is, thevariations of the balloon can affect the movement of adjacent vertebrae.For example, a less compressible balloon will increase stability butfurther restrict movement of the vertebrae; a more compressible balloonwill provide more movement and mobility.

In the alternate embodiment of FIG. 9, the metal support strip 160,shown rectangular in cross section, is positioned inside the open arms135, 137 of implant 130. The surface 152 of the balloon 150 is attachedto the strip 160. The opposite surface 162 of the strip is attached tothe inner surface of hinged sections 132. Metal strip 160 functions in asimilar manner to strip 48 of FIG. 3.

FIG. 10 illustrates an alternate way to connect the implant units(sections) 230. Two engaging closed loops 232, 234 are linked to providethe attachment. This connection provides for movement of adjacentsections 230, while maintaining the inter-lock. It also helps tomaintain the linked sections 32 in the curved configuration.

It is also contemplated that the support 48 (or 160) constitutes theelement for moving the hinged sections to the curved configuration, withthe balloon being moved to its curved shape by the hinged sections 32and then maintaining the shape and support of the sections.Alternatively, the balloon can be the sole element moving the hingedsections 32 to the curved shape, with the support following the movementof the sections 32 to subsequently support the sections. Alternatively,both the balloon and support 48 (or 160) cooperate together to move andmaintain the hinged sections.

Each of the implants assumes a substantially straightened configurationfor delivery to the surgical site. Once delivered to the disc space, thehinged sections and the inflated balloon provide sufficient springinessin response to vertebral loads placed on the device by the spine. Thisprovides both support for the vertebral bodies plus the desiredflexibility. As noted above, variations in the balloon can vary thesupport and flexibility for the vertebral bodies.

Any of the foregoing implants can be provided with a roughened surface,such as a textured surface, to enhance bone ingrowth to enhance implantretention in the disc space. Surface finishes such as hydroxyapatite,calcium silicate and calcium phosphate could also be applied to allowfor bone ingrowth.

In use, the disc nucleus is removed arthroscopically, i.e. throughcannula 14, by device 10. Cannula 14 can optionally be placed by firstinserting a needle and wire, removing the needle and sequentiallyplacing and removing dilators of progressively increasing diameter overthe wire until the desired cannula diameter is reached. After removal ofthe disc, device 10 is withdrawn through cannula 14 and then a deliverydevice, containing any of the foregoing implants, is inserted throughthe cannula. The implant is contained within the delivery device in asubstantially straightened configuration with the balloon in thecollapsed (unexpanded) configuration. The implant is then ejected fromthe delivery device and implanted in the disc space between thevertebral bodies, with the balloon filled to expand and maintain thecurved configuration. The delivery instrument and cannula 14 arewithdrawn from the body. FIG. 8 illustrates the implant 30 positionedwithin the disc space.

While the above description contains many specifics, those specificsshould not be construed as limitations on the scope of the disclosure,but merely as exemplifications of preferred embodiments thereof. Forexample, in addition to the substantially C-shaped cross-sectionalconfigurations, substantially circular, rectangular, hexagonal,substantially octagonal as well as other configurations arecontemplated. Also the length of the implant could be longer than thatshown in the drawings for assuming the curved shape. Those skilled inthe art will envision many other possible variations that are within thescope and spirit of the disclosure as defined by the claims appendedhereto.

1. A spinal implant comprising a series of sections hinged together anda balloon connected to the sections, the balloon having a curvedconfiguration, the implant having a first delivery configuration and asecond curved configuration, the implant having a more linearconfiguration in the first delivery configuration than in the secondcurved configuration, the implant assuming the first deliveryconfiguration during delivery to the disc space and maintaining thesecond curved configuration after placement within the disc space andexpansion of the balloon.
 2. The spinal implant of claim 1, wherein theimplant is substantially C-shaped in the curved configuration.
 3. Thespinal implant of claim 1, wherein the implant further comprises asupport strip connected to the hinged sections.
 4. The spinal implant ofclaim 1, wherein the support strip is positioned on an outer surface ofthe hinged sections.
 5. The spinal implant of claim 1, wherein thesupport strip is positioned between the balloon and the hinged sections.6. The spinal implant of claim 1, wherein the hinged sections are linkedby a ball and groove arrangement.
 7. The spinal implant of claim 1,wherein the hinged sections are linked by interlocking closed loops. 8.The spinal implant of claim 1, wherein the implant includes a texturedsurface to enhance frictional engagement with the vertebral bodies. 9.The spinal implant of claim 1, wherein the hinged sections include anopening defined by arms to receive a portion of the balloon.
 10. Thespinal implant of claim 3, wherein the support strip is composed ofshape memory material and has a memorized curved configuration.
 11. Thespinal implant of claim 1, wherein the balloon in the expandedconfiguration has a first area and a smaller area having a smallertransverse cross section, each area extending along a length of theballoon.
 12. The spinal implant of claim 11, wherein the smaller area isreceived within an opening in the hinged sections.
 13. The spinalimplant of claim 12, further comprising a support strip attached to thehinged sections and extending along a length thereof.
 14. A method ofminimally invasively inserting a spinal implant in a disc spacecomprising: providing a delivery instrument containing the spinalimplant in a first configuration, the spinal implant having a pluralityof hinged sections and a balloon connected thereto; inserting thedelivery instrument to the disc space; deploying the implant from thedelivery instrument to position the implant in the disc space; expandingthe balloon to maintain the hinged sections in a substantially horseshoeshaped configuration; and removing the delivery instrument and leavingthe implant in place.
 15. The method of claim 14, wherein the implantincludes a support strip, and the step of deploying the implant enablesthe support strip to move to a substantially horseshoe shape.
 16. Themethod of claim 14, wherein the step of expanding the balloon expandsthe hinged sections in a direction transverse to a plane of the discspace.
 17. The method of claim 14, wherein the spinal implant is in asubstantially straightened configuration in the first configuration.